1. Field of the Invention
The invention relates to a drum for holding and moving a particulate material which serves in particular for forming a drug.
2. Description of the Prior Art
A device disclosed in U.S. Pat. No. 4,543,906 for coating particles has a drum, rotatable about an axis, for holding and moving a particulate material. The drum has a cylindrical walled section with perforation holes. In devices known on the market and formed approximately according to the stated patents, said perforation holes have internal diameters of about 2.5 mm to 4 mm. In the production of drugs, however, it is frequently necessary to process particles whose diameters are less than 2.5 mm and, for example, about 0.2 mm to 1 mm. To ensure that such small particles do not fall out of the drum through the perforation holes, at least one textile fabric is detachably fastened by means of holders in the drum. However, during movement and treatment of fine particles, it is virtually unavoidable that particles and abraded material therefrom pass between the fabric and the wall of the drum. In the production of drugs, the purity of the products has to meet high requirements. The devices must therefore be cleaned frequently and in particular when the product is changed. The holders and the fabric must be removed from the drum, the drum, the holders and the fabric must be separately cleaned and the fabric and the holders must then be installed in the drum again. This requires a great deal of time and makes the operation of the devices more expensive. Furthermore, the textile fabrics are easily damaged during use and during removal from the drum, washing and reinsertion into the drum and must in practice be replaced after a very short time.
A device disclosed in Soviet Inventor's Certificate 1 275 065 for granulating slag has an inclined, perforated drum which is covered by a mesh. From the document cited, it is not evident what the mesh consists of and where and how the mesh is fastened. It therefore appears plausible that this granulating device has disadvantages similar to those of the devices described before, in which a textile fabric is detachably fastened by means of holders.
Japanese Patent Application Publication 59 091 865 discloses a device for the production of granular seaweed. The device has a drum with a perforated wall and a corrugated louver arranged on its inside. Said louver is formed from a net plate having holes. Since the louver is corrugated, it can rest against the wall of the drum at most at the wave summits. Cavities in which processed material, i.e. seaweed and any other material introduced for processing, can collect are therefore present between the wall and the louver. Cleaning of the drum is therefore difficult, complicated and time-consuming. Moreover, the English Abstract does not reveal the material of which the louver consists and where and how it is fastened.